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Re: starship-design: Anti-antimatter

L. Clayton Parker writes:
 > > Of course, with a quantum black hole you can do partial conversion of
 > > mass to energy by feeding it at the same rate that it emits mass/energy
 > > due to quantum evaporation.  If you run out of fuel you have to be able
 > > to toss the black hole away before it blows up due to runaway
 > > evaporation; the rate of evaporation is inversely related to the mass of
 > > the black hole.
 > (P.S. at least on argument says the black hole will ALWAYS evaporate
 > QUICKLY and therefore it is useless to attempt this...)

On the other hand, if you can get the right evaporation rate and
maintain it, you also get the advantage that the evaporation products
will be statistically 1/2 matter and 1/2 antimatter (except for the
photons).  So if it is possible to keep a quantum black hole just on the
edge of evaporation at a rate useful for propulsion and power
generation, you also get near-total matter-to-energy conversion by
recombining the evaporation products.

My understanding is that evaporation rate is a function of the mass of
the black hole (and hence the gravity gradient near it), with the rate
going up asymptotically as the black hole mass approaches zero.  You
also have the problem that radiation pressure from the evaporating black
hole will make it difficult to pump more mass into it to prevent runaway
evaporation, especially as you want more power.  Unfortunately I don't
know the exact equation that relates evaporation rate to mass to know
whether it would be feasible to keep a quantum black hole in a stable
state and get a useful power output.